The present disclosure relates to a charger for charging a secondary battery of a portable terminal or the like as well as to an electronic apparatus system including the charger.
Chargers capable of charging an electronic apparatus including portable ones are now available in a variety of shapes. A secondary battery incorporated in an electronic apparatus is charged by connecting a charger to the electronic apparatus. Various proposals have been made to secure the safety during charging (refer to JP-A-8-308139, JP-A-2007-195021, JP-A-2007-325500, for example).
In JP-A-8-308139, a constant current regulation circuit, a constant voltage regulation circuit, a control unit, etc. are provided in a charger. For quick charging of a secondary battery, the danger due to heat generation by the secondary battery is lowered by setting thermal cutoff temperature stages according to the temperature of the secondary battery.
In JP-A-2007-195021, a portable terminal apparatus is equipped with an authentication circuit, a built-in power source for supplying power to the authentication circuit, and a power managing means for shutting off the supply of power from an external power source to the terminal main body and supplying power to the authentication circuit from the built-in power source during authentication of the external power source. The terminal main body can be protected by abstaining from using an external power source to be authenticated, and power consumption of the built-in power source that is used for authentication can be reduced by supplying power from it only during an authentication period.
In JP-A-2007-325500, a power supply device is equipped with a receiving means for receiving internal temperature data of a charging/discharging device, a temperature measuring means for measuring its own internal temperature, and a power supply mode switching means for switching the mode of power supply to the charging/discharging device on the basis of the internal temperature data. A battery pack can be charged in a charging mode that is suitable for a temperature condition by measuring its temperature. This makes it possible to suppress charging capacity reduction due to an overcurrent that occurs when the battery pack is charged in a state that its temperature is out of a proper range.
To secure the safety during charging, proposals have been made in which a threshold value is set in the temperature range of a secondary battery or the like for its charging (refer to JP-A-8-308139, JP-A-2007-195021, JP-A-2007-325500). However, whereas the connection units between chargers and electronic apparatus are being miniaturized, no techniques have been proposed which take into consideration the situation that the danger due to heat generation that is caused by short-circuiting that is induced by dust, water, etc. is increasing.